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High Flow Cats and O2 sensor

 
  #1  
Old 11-18-2015, 10:53 AM
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High Flow Cats and O2 sensor

Hello, im looking to install high flow cats
https://www.rpmoutlet.com/powercats.htm

Amazon.com: MagnaFlow 49 State Converter 99659HM 99000 Series; Universal Catalytic Converter; Heavy Metal Loaded; 3 in. Inlet/Outlet; Center/Center; Round; L-3 in.; W-5 in.; Overall Length 8.75 in.; 49 State;: Automotive Amazon.com: MagnaFlow 49 State Converter 99659HM 99000 Series; Universal Catalytic Converter; Heavy Metal Loaded; 3 in. Inlet/Outlet; Center/Center; Round; L-3 in.; W-5 in.; Overall Length 8.75 in.; 49 State;: Automotive

My concern is it would appear that the rear O2 sensors are directly in the stock cats. It seems my options are:

1.Get the HF cats and drill a bung in the pipe after the cats and install O2 sensor (still throw a code?)
2. Get the HF cats and do nothing with O2 sensor and get tune (fail emissions still)?
3. Leave stock cats because of PIA!!!

I have 80k on truck and have removed resonators with a cutout. Looking for a little more sound and possibly performance without jumping into headers.

Thanks.
 
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Old 11-18-2015, 11:13 AM
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As I understand it the rear(cat) O2 sensors do nothing but tell the computer if the cats are doing their job, hence the 'cat below threshold efficiency' code for removing them. So I would think in theory having the sensor right after the aftermarket cats shouldn't throw a code as long as those high flow cats are actually doing what they are supposed to.

Any aftermarket tune or tuner like a SCT can simply turn the rear O2 sensors off and no codes.

I run no cats with no codes with an aftermarket custom tune. And have no issues with the truck whatsoever.

We have no emission testing here. Woohoo, true north strong and free!
 
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Old 11-18-2015, 11:20 AM
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Ha, you are lucky! Thanks for the response. Do you have rasp after removing the cats?
 
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Old 11-18-2015, 12:18 PM
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just go with the headers, hf cats... sensor kits. or be happy with what you have now.

bits at a time.. end up costing a lot more. at the finish line.

and talk to the company that make the headers... for there choice of cats and sensors.. they have already done the work...
 
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Old 11-18-2015, 10:09 PM
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I don't find my exhaust raspy at all and I'm familiar with what it is as I used to have a 350z with no cats as well and that sucker was raspy. The truck is tame. A little louder at start up and under WOT but dead quiet at a warm idle and under normal driving conditions. No drone whatsoever. The rest of my exhaust is stock and I'm hesitant to pull out a resonator/muffler as I dislike cab noise at highway speeds.

I don't think there's much of anything to be gained on these trucks with shorty headers, similar to the 5.4's. My manifolds don't leak and I'd never willingly open that potential can of worms. I've had headers on other motors and always end up getting to know the gasket install and torque procedure too well it seems.
 
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Old 11-19-2015, 10:30 AM
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I agree with shorty headers. so if i did it it would be long and that is expensive an all fronts. I think i will try the HF cats and weld a bung down pipe. If the rear O2 sensors are just there to tell if the cat is working correctly, then i can always get a tune to disable them.
 
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Old 11-19-2015, 10:54 AM
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Yup. Mytruckruns flawlessly with the rear o2's disabled. No codes, and turned off in a custom tune done by a speed shop up here that has their own dynos. Lightspeed innovations in Red Deer. I have also noticed it as an option on the SCT 'canned tunes' to disable rear O2 sensors.
 
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Old 12-14-2015, 02:35 PM
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Hate to drum up a dead post, but you are wasting your money. This isn't the 70s, your stock cats will outflow a stock engine especially with stock manifolds. Removing them will increase noise and that's about it and cause you greif if you have emissions inspections.
 
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Old 12-14-2015, 09:58 PM
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I don't think the shop that custom dyno tuned my truck would agree with you but suite yourself if you think a motor that cranks 6k rpm is breathing fine through stock cats.
 
  #10  
Old 12-15-2015, 11:58 AM
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Won't argue an aftermarket should outflow stock. The factory manifolds won't outflow the converters.
 
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Old 12-15-2015, 01:45 PM
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I wonder where you got that info or why you would think that?
 
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Old 12-16-2015, 01:44 PM
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I don't follow numbers for the 6.2 because I don't really care to. My point to you is you are likely wasting your money on a set of converters because of 1 person's opinion. Forced induction this would be a different story. To truely compare converters you need to know the cell count of the substrate, surface area, diameter and so on. Until you know what is in there stock, the aftermarket set could actually flow worse. If you are that worried about all out performance lose them. Anything in the exhaust system is a restriction, pipe length, bends, mufflers, converters, you get the idea. In the end even if you cut them off you aren't going to notice the 10 horsepower it gained on the top end, especially in a truck.
 
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Old 12-16-2015, 08:53 PM
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You misunderstood my previous posts. I have no cats on my truck, whatsoever. My truck was tuned on a dyno taking this into consideration. I do enjoy running my truck WOT unloaded. Maybe more so than others.
 
 
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